<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>改变按钮</title>
    <style>
        #but{
            color: blue;
        }
    </style>
</head>
<body>

    <input type="button" id="but"onclick="f()" value="点我就变" >

</body>
</html>
<script>
    //1. 点击按钮时，改变按钮上字体的颜色和大小
    function f() {
        var but = document.getElementById("but");
        but.style.fontSize="250px"
        but.style.color="red"
    }


</script>